Apparatuses and Methods for Processing Doses of Flowable Material

ABSTRACT

An apparatus comprises an extruding device ( 2 ) having a dispensing opening ( 8 ) for extruding a flowable material along an exit direction (Z 1 ) through said dispensing opening ( 8 ), and cutting means ( 3 ) for separating a dose ( 50 ) from said flowable material, said cutting means ( 3 ) being movable with a motion component that is parallel to said exit direction (Z 1 ).

The invention relates to apparatuses and methods for obtaining doses offlowable material, in particular doses of plastics, by cutting flowablematerial exiting from an extruding device. The doses thereby obtainedcan be processed by compression-moulding to obtain objects, particularlypreforms for containers such as bottles.

The invention furthermore relates to apparatuses and methods fordiscarding possible defective doses so as to prevent such doses frombeing compression-moulded.

An apparatus is known for compression-moulding doses of plastics,comprising an extruding device from which the plastics exit along anexit direction. The apparatus furthermore comprises cutting means forseparating the doses from the plastics exiting from the extrudingdevice. The cutting means comprises a plurality of knives rotatinglymobile around an axis parallel to the exit direction. Each knife isprovided with a blade that extends on a plane perpendicular to the exitdirection and keeps on this plane during rotation.

The plastics exit from the extruding device in a continuous manner. Thuswhilst a knife is cutting a dose, the portion of plastics from which apart of the dose has already been separated continues to exit from theextruding device. This portion of plastics tends to stick to the blade,cooling prematurely, and exerts on the knife a thrust that may deformthe blade, compromising cutting precision.

U.S. Pat. No. 4,640,673 discloses a particular type of apparatus forcompression-moulding doses of plastics, which is provided with anextruding device and with a pair of knives rotatable around a rotationaxis that cut the plastics exiting from the extruding device at presetintervals, so as to separate doses of plastics.

The knives rotate around the rotation axis at an angular speed thatvaries according to a preset law. In particular, the angular speed ofthe knives is relatively high when the knives separate the doses fromthe plastics exiting from the extruder. Immediately after cutting thedoses, the angular speed of the knives is decreased. In order to movethe knives at a variable angular speed, the apparatus disclosed in U.S.Pat. No. 4,640,673 comprises a pair of elliptical toothed wheelsinterposed between the knives and a motor that rotates the knives. Theelliptical toothed wheels are designed in such a way as to ensure thatthe angular speed of the knives varies according to the desired law.

A drawback of the apparatus disclosed in U.S. Pat. No. 4,640,673 is thatit is not very versatile. In fact, if it is desired to modify the lawaccording to which the angular speed of the knives is varied, forexample because the plastics to be extruded or the temperature thereofhave been changed, or because it is desired to modify the length of thedoses, it is necessary to dismantle the previously used pair ofelliptical toothed wheels and replace the latter with a new pair ofelliptical toothed wheels that drive the knives at the desired angularspeed. This operation, in addition to requiring the arrest of theapparatus, is rather complicated and very time-consuming. A furtherdrawback of known apparatuses is that the cutting means has surfaces towhich the plastics, that are in a pasty state when they exit from thedispensing device, tend to adhere during cutting. These adhesionphenomena in fact impair the performance of a precise and clean cut ofthe plastics and lead to the creation of defective doses. Furthermore,the adhesion of the plastics, that are at a high temperature, causessignificant wear to the knives, which thus have to be changedfrequently, with consequent increase in the running costs of theapparatus.

An object of the invention is to improve known apparatuses and methodsfor obtaining doses of flowable material, in particular by increasingprecision and efficiency in cutting. Another object is to obtain anapparatus and a method that enable doses to be cut in a clean andprecise manner from a flowable material exiting from an extrudingdevice.

Still another object is to enable the speed of the cutting means to bevaried in a simple and rapid manner, even if the law has to be changedaccording to which the speed of the cutting means varies.

A further object is to provide a method that enables doses of flowablematerial to be cut in a rapid manner.

Still another object is to reduce considerably the phenomena of adhesionof the flowable material to the cutting means.

A further object is to improve the apparatuses for discarding possibledefective doses of flowable material.

In a first aspect of the invention, an apparatus is provided comprisingan extruding device having a dispensing opening for extruding a flowablematerial along an exit direction through said dispensing opening, andcutting means for separating a dose from said flowable material,characterised in that said cutting means is movable with a motioncomponent that is parallel to said exit direction.

In a second aspect of the invention, a method is provided comprisingextruding a flowable material along an exit direction and separating adose from said flowable material through cutting means, characterised inthat said separating comprises moving said cutting means with a motioncomponent that is parallel to said exit direction.

Owing to these two aspects of the invention, it is possible to obtain anapparatus and a method that enable precise and clean cutting of theflowable material exiting from the dispensing device. The motioncomponent along the exit direction causes the cutting means to move awayfrom the portion of flowable material exiting from the extruding devicefrom which part of the dose has already been separated. This minimisesthe contact between the cutting means and the flowable material. Risksof adhesion of the flowable material to the cutting means are thusreduced. Furthermore, the flowable material is not prematurely cooleddue to the contact with the cutting means. Lastly, the pressure isreduced that is exerted on the cutting means by the flowable materialexiting from the extruding device, which makes deforming of the cuttingmeans more difficult.

In a third aspect of the invention, an apparatus is provided comprisingan extruding device for extruding a flowable material, cutting meansthat is movable along a path for separating a dose from said flowablematerial, driving means for moving said cutting means at a variablespeed along said path, characterised in that said driving meanscomprises electronic speed-varying means.

Owing to the third aspect of the invention, it is possible to obtain avery versatile apparatus in which the law according to which the speedof the cutting means varies can easily be modified. In particular, if itis necessary to modify the manner in which the speed of the cuttingmeans varies because, for example, the flowable material or thetemperature thereof has been changed, or again the dimensions of thedose have been changed, it is sufficient to reprogram the electronicspeed-varying means. This may occur in a very rapid manner inasmuch asit is not necessary to replace mechanical parts of the apparatus, as wason the other hand required by prior-art apparatuses. Further, theelectronic speed-varying means enables the speed of the cutting means tobe kept constant within a desired interval, for example whilst theflowable material exiting from the extruding device is cut. This was notpossible with the elliptical toothed wheels disclosed in U.S. Pat. No.4,640,673.

In a fourth aspect of the invention, a method is provided comprisingextruding a flowable material, moving cutting means along a path at aspeed for separating a dose from said flowable material, modifying saidspeed along said path, characterised in that said modifying comprisesmaking said speed different from greater than zero.

In an embodiment, said modifying comprises making this speed equal tozero. This means that the cutting means is arrested along the paththereof.

In a further embodiment, said modifying comprises making said speed lessthan zero. This means that the cutting means is moved backwards.

Owing to this aspect of the invention, it is possible to cut the dosesof flowable material in a fast and clean manner. By stopping or movingbackwards the cutting means when the latter is not cutting the dose, itis possible to increase the duration of the interval in which thecutting means does not interact with the flowable material. This enablesthe duration of the interval to be reduced in which cutting meansinteracts with the flowable material and consequently enables the speedwith which the dose is cut to be increased. In this way, the cut is madein a clean manner, which reduces the risk of burrs forming, which burrscrystallise easily and can cause defects on the moulded object.

In a fifth aspect of the invention, an apparatus is provided comprisingan extruding device for extruding a flowable material, cutting means forseparating a dose from said flowable material, a cooling circuit forcooling said cutting means, characterised in that said cutting meanscomprises a first laminar part and a second laminar part between whichthere is defined conduit means of said cooling circuit.

Owing to the fifth aspect of the invention, it is possible to obtain anapparatus that enables phenomena of adhesion of the flowable material tothe cutting means to be reduced considerably when the dose is beingseparated from the flowable material exiting from the extruding device.The conduit means identified between the first laminar part and thesecond laminar part in fact enables the temperature of the externalsurfaces of the cutting means to be reduced effectively and consequentlythe adhesion of the flowable material to be reduced.

In a sixth aspect of the invention, an apparatus is provided comprisingan extruding device for extruding a flowable material, cutting means forseparating a dose from said flowable material, said cutting means havingan operating surface suitable for interacting with said flowablematerial, characterised in that said cutting means is provided withheating means for heating said operating surface.

In a seventh aspect of the invention, a method is provided comprisingextruding a flowable material, separating a dose from said flowablematerial through cutting means, characterised in that it furthermorecomprises heating said cutting means.

Owing to the sixth and seventh aspect of the invention, it is possibleto diminish adhesion of the flowable material to the cutting means whenthe latter interacts with the flowable material to separate the doses.

In fact, by heating the cutting means to a temperature slightly greaterthan the melting temperature of the flowable material to be cut, theflowable material is prevented from solidifying on contact with thecutting means. This prevents solid residues of the flowable materialfrom accumulating on the cutting means. If on the other hand the cuttingmeans is heated to a temperature much greater than the meltingtemperature of the flowable material, possible residues of flowablematerial accumulated on the cutting means are degraded or volatilizedthermally, which enables the cutting means to be kept substantiallyclean.

In an eighth aspect of the invention, an apparatus is providedcomprising an extruding device having a dispensing opening for extrudinga flowable material along an exit direction through said dispensingopening, cutting means for separating a dose from said flowable materialand discarding means for discarding a possible defective dose,characterised in that said discarding means comprises diverting meansfor diverting said possible defective dose from said exit direction.

In a ninth aspect of the invention, a method is provided comprisingextruding a flowable material along an exit direction, separating a dosefrom said flowable material, discarding a possible defective dose,characterised in that said discarding comprises diverting said possibledefective dose from said exit direction.

Owing to the eighth and ninth aspects of the invention, it is possibleto obtain an apparatus in which possible defective doses are discarded,in a simple and efficient manner, immediately after being separated fromthe extruded flowable material. In this way the defective doses,particularly if they have dimensions such as not to be transportable,are prevented from reaching transferring means arranged downstream ofthe cutting means, causing the apparatus to stop.

In a tenth aspect of the invention, an apparatus is provided comprisingtransferring means for transferring a dose of flowable material from aremoving position to a delivering position, receiving means forreceiving said dose in said delivering position, discarding means fordiscarding a possible defective dose, characterised in that saiddiscarding means is arranged upstream of said delivering position.

In an eleventh aspect of the invention, a method is provided comprisingtransferring a dose of flowable material from a removing position to adelivering position, receiving said dose in said delivering position,discarding a possible defective dose, characterised in that saiddiscarding occurs upstream of said delivering position.

Owing to the tenth and to the eleventh aspect of the invention, it ispossible to optimise the position of the discarding means along thetransferring means. Having positioned the discarding means upstream ofthe delivering position prevents the transferring means having to bepurposely slowed to discard possible defective doses. In fact, upstreamof the delivering position the transferring means already moves per sewith relatively low acceleration, in order not to stress the doseexcessively that it is transferring. On the other hand, downstream ofthe delivering position, when the dose has already been released to thereceiving means, the transferring means moves with greater accelerationto which the discarding means poses no limit.

The invention can be better understood and implemented with reference tothe attached drawings, which illustrate some exemplifying andnon-limiting embodiments thereof, in which:

FIG. 1 is a perspective view of a portion of an apparatus forcompression-moulding of doses of plastics;

FIG. 2 is a plan view of the apparatus in FIG. 1;

FIG. 3 is a partially sectioned schematic front view showing cuttingmeans for cutting a dose of plastics in an initial cutting step;

FIG. 4 is a view like the one in FIG. 3, showing the cutting means in afinal cutting step;

FIG. 5 is a schematic frontal view of cutting means according to analternative embodiment;

FIG. 6 is a schematic view showing the geometrical arrangement of thecutting means in FIG. 5;

FIG. 7 is a graph that shows schematically how the speed of the cuttingmeans in FIG. 5 varies, in a first embodiment;

FIG. 8 is a graph that shows schematically how the speed of the cuttingmeans in FIG. 5 varies, in a second embodiment;

FIG. 9 is a graph that shows schematically how the speed of the cuttingmeans in FIG. 5 varies, in a third embodiment;

FIG. 10 is a perspective view showing a knife of the cutting means inFIG. 5;

FIG. 11 is a perspective view that shows a first laminar part of theknife in FIG. 10;

FIG. 12 is a perspective view that shows a second laminar part of theknife in FIG. 10;

FIG. 13 is a view like the one in FIG. 1 that shows an apparatusaccording to an alternative embodiment comprising diverting means fordiscarding a possible defective dose exiting from an extruding device;

FIG. 14 is an enlarged view of the diverting means in FIG. 13;

FIG. 15 is a plan view of transferring means of the apparatus in FIG. 1,associated with discarding means.

With reference to FIGS. 1 and 2, there is shown an apparatus 1 forcompression-moulding doses 50 of plastics so as to obtain objects, suchas, for example, preforms for containers, particularly for bottles. Theapparatus 1 comprises an extruding device 2 provided with a dispensingopening 8 through which the plastics are extruded along an exit axis Aarranged in an exit direction Z1.

The apparatus 1 furthermore comprises cutting means 3 that cuts theplastics exiting from the extruding device 2 to separate the doses 50therefrom.

Below the cutting means 3 transferring means 9 is provided fortransferring the doses 50 cut by the cutting means 3 to forming means 17comprising a plurality of moulds 20 mounted in a peripheral region of amoulding carousel 26. Each mould 20 comprises a die 21 and a punch thatis not shown, which are movable with respect to one another between anopen position in which a dose 50 can be inserted inside the die 21, anda closed position in which the dose 50 is shaped so as to obtain apreform. The latter is extracted from the mould 20 by means of anextracting device 60.

The transferring means 9 comprises first transferring means 100comprising a first carousel 23 that is rotatable around a rotation axisZ2. In a peripheral region of the first carousel 23 a plurality of firsttransferring elements 101 is mounted, each one of which has a crosssection having a “C”-like shape and is provided with a concavity inwhich a dose 50 can be received. Below this concavity a funnel elementis provided that is not shown, through which the dose 50 can betransferred to second transferring means 24 of the transferring means 9.

The second transferring means 24 comprises a plurality of secondtransferring elements 27, each of which has the shape of a hollowcylinder. Each transferring element 27 is provided with a lower end thatcan be shut or opened through closing means that is not shown.

The first transferring elements 101 are movable along a substantiallycircular first path P1, along which each first transferring element 101receives the dose 50 cut by the cutting means 3 in a removing position Qshown in FIG. 1. Whilst the first transferring element 101 moves alongthe first path P1, the dose 50 descends by gravity along the walls ofthe first transferring element 101 and, after passing through thecorresponding funnel element, is delivered to a second transferringelement 27.

The second transferring elements 27 are movable along a second path P2that is at a lower level than the first path P1. Whilst it moves alongthe second path P2, each second transferring element 27 receives thedose 50 from a first transferring element 101 that is above and, in adelivering position R, releases the dose 50 inside an underlying die 21.The latter moves along a substantially circular third path P3 arrangedat a lower level than the second path P2.

As shown in FIG. 1, the cutting means 3 is provided with a knife 22comprising a blade 4 supported by a supporting element 5. The blade 4has a substantially flat geometry and is provided with a cutting edge53, having a substantially rectilinear shape, which lies on the planedefined by the blade 4. The knife 22 is rotated through driving means 7in such a way as to pass periodically below the extrusion opening 8 tocut the plastics exiting from the extruding device 2.

FIGS. 3 and 4 show an alternative embodiment of the apparatus 1, inwhich the knife 22 is moved in a rectilinear manner instead of beingrotated as shown in FIG. 1. The plastics are dispensed by the extrudingdevice 2 in a continuous manner and move along the exit axis A in theexit direction Z1 at a substantially constant exit speed V. The blade 4moves along a rectilinear trajectory T that is contained on a plane thatis oblique with respect to the exit axis A. In other words, the blade 4has a motion component that is parallel to the exit direction Z1 and afurther motion component that is perpendicular to the exit direction Z1.The motion component that is parallel to the exit direction Z1 isdirected from the dispensing opening 8 to the first transferring means100.

FIG. 3 shows the knife 22 in an initial cutting step, in which the blade4 has reached the plastics and starts to separate the dose 50 from aninitial portion Q1 of plastics. Whilst the blade 4 continues to cut theplastics, the initial portion Q1 moves along the exit direction Z1moving away from the dispensing opening 8. Also the blade 4, by movingalong the trajectory T, moves away from the dispensing opening 8 sothat, in a final cutting step shown in FIG. 4, the blade 4 separates thedose 50 from a final portion Q2 of the plastics that is roughly at thesame level as the initial portion Q1, in a position diametricallyopposite the initial portion Q1.

In this way it is possible to obtain doses 50 of plastics that aredelimited by a side surface 28 and by two end surfaces 29, in which theend surfaces 29 are substantially orthogonal to the side surface 28.

The blade 4 moves at a speed W having a cutting component W1 that isperpendicular to the exit direction Z1 and a pursuing component W2 thatis parallel to the exit direction Z1. The cutting component W1 enablesthe blade 4 to separate the dose 50 from the plastics exiting from thedispensing opening 8, whilst the pursuing component W2 enables the blade4 to move in the same direction as the plastics during cutting. Thepursuing component W2 can be greater than, or the same as, the exitspeed V of the plastics from the extruding device 2. If the pursuingcomponent W2 is greater than the exit speed V of the plastics, the blade4 tends to tear the dose 50 from the plastics exiting from thedispensing opening 8, which makes it easier to separate the doses 50from the plastics.

The contact between the cutting means 3 and the plastics is alsominimised, because if the pursuing component W2 is greater than the exitspeed V, the plastics come into contact substantially only with thecutting edge 53 of the blade 4. This enables the thrust to be reducedthat the plastics exiting from the dispensing opening 8 exert on theblade 4. In other words, the initial portion Q1 substantially does notpush down the blade 4, because the blade 4 moves away from thedispensing opening 8 together with, or even a little faster than, theinitial portion Q1. Deformations of the blade 4 are thus avoided thatare due to the thrust exerted by the plastics exiting from thedispensing opening 8, which enables good cutting precision to bemaintained. Furthermore, it is more difficult for the plastics exitingthe dispensing opening 8 to adhere to the blade 4. Lastly, cooling ofthe plastics in contact with the blade 4 is less.

FIG. 5 shows an embodiment of the apparatus 1 in which the cutting means3 is rotated by the driving means 7, as already disclosed with referenceto FIG. 1, and move away from the dispensing opening 8 during cutting.The driving means 7 comprises an electric motor 31, provided with amotor shaft 32 that extends along a longitudinal axis L. The electricmotor 31 is fixed to a flange 33 by means of a clamp 34 clamped on themotor shaft 32. The flange 33 is in turn fixed, through fixing meansthat is not shown, to a supporting bracket 35 mounted on a frame 36 ofthe apparatus 1. Between the flange 33 and the supporting bracket 35there is interposed a spacer 37, delimited by a first face 38 facing theflange 33 and by a second face 39 facing the supporting bracket 35. Asthe first face 38 and the second face 39 are not parallel to oneanother, the flange 33, which is substantially perpendicular to themotor shaft 32, can be tilted with respect to the supporting bracket 35.The latter defines a resting plane for the spacer 37 that issubstantially perpendicular to the exit axis A. The spacer 37 thusenables the longitudinal axis L of the motor shaft 32 to be tilted withrespect to the exit axis A along which the plastics exiting from theextruding device 2 move.

On the motor shaft 32 there is mounted the knife 22 by means of afurther spacer 40 interposed between a first plate 43 and a second plate44. The first plate 43 is fixed to the motor shaft 32 so as to besubstantially perpendicular to the longitudinal axis L. The second plate44 is fixed to the supporting element 5 of the knife 22 and issubstantially parallel to a plane defined by the blade 4. The furtherspacer 40 is delimited by a first surface 45, which is in contact withthe first plate 43, and by a second surface 46, which is in contact withthe second plate 44. The first surface 45 and the second surface 46 aretilted with respect to one another. Thus the further spacer 40 enablesthe knife 22 to be mounted on the motor shaft 32 in such a way that anaxis H, which is perpendicular to the plane defined by the blade 4, isnot parallel to the longitudinal axis L of the motor shaft 32. In otherwords, owing to the further spacer 40 the blade 4 lies on a plane thatis oblique with respect to the longitudinal axis L.

The arrangement of the longitudinal axis L, of the axis H and of theexit axis A shown in FIG. 5 can be better understood by examining theFIG. 6. In the FIG. 6, there has been defined a Cartesian referencesystem XYZ in which the plane XY coincides with the plane defined by theblade 4 in the theoretical case in which the blade 4 lies on a planethat is perpendicular to the exit direction Z1 and rotates maintainingitself on this plane. The plane XZ contains the exit axis A and thelongitudinal axis of the motor shaft in the theoretical case in whichthe blade 4 lies on a plane that is perpendicular to the exit directionZ1 and rotates by maintaining itself on this plane. The Cartesian axis Zis thus parallel to the exit axis A along which the plastics exitingfrom the extruding device 2 move. The origin O of the Cartesianreference system XYZ was selected as an intersecting point between thelongitudinal axis of the motor shaft and the plane on which the blade 4lies, in the theoretical case in which the blade 4 lies on a planeperpendicular to the exit direction Z1 and rotates by maintaining itselfon this plane. To obtain the situation shown in FIG. 5, it is assumedthat the longitudinal axis L of the motor shaft 32 and the axis H rotatearound the origin O. The axis H shown in FIG. 6 is therefore the axispassing through the origin O and orthogonal to the plane on which theblade 4 lies in the configuration shown in FIG. 5.

It should be noted that the longitudinal axis L and the axis Hintersect, despite not being parallel to one another. The exit axis A ison the other hand skew with respect to the longitudinal axis L and tothe axis H.

It is possible to define a plane π, which contains the Cartesian axis Zand the longitudinal axis L. The plane π forms a first angle σ with theCartesian plane XZ, whilst the longitudinal axis L of the motor shaft 32forms, on the plane π, a second angle ρ with the Cartesian axis Z. Thefirst angle σ and the second angle ρ enable the position of thelongitudinal axis L in the Cartesian reference system XYZ to be definedcompletely.

It is furthermore possible to define a further plane π′, which containsthe longitudinal axis L and the axis H. The plane π and the furtherplane π′ intersect along the longitudinal axis L. The further plane π′is obtained by rotating the plane it by a third angle φ around thelongitudinal axis L. On the further plane π′, the axis H that isperpendicular to the plane defined by the blade 4 forms a fourth angle ξwith the longitudinal axis L of the motor shaft 32. The third angle φand the fourth angle ξ enable the position of the axis H to be definedcompletely with respect to the longitudinal axis L.

During operation, the electric motor 31 rotates the knife 22 around thelongitudinal axis L, so that the blade 4 moves along a closed-loop pathand interferes periodically with the plastics exiting from the extrudingdevice 2. The arrangement of axes shown in FIGS. 5 and 6 ensures thatthe blade 4, when interacting with the plastics, has a motion componentdirected along the exit direction Z1 and a further motion component thatis perpendicular to the exit direction Z1. In this way the blade 4,whilst cutting the plastics, moves away from the dispensing opening 8and accompanies the dose 50 that moves along the exit direction Z1. Thisenables more precise doses to be obtained and a cleaner cut to beobtained, as disclosed previously with reference to FIGS. 3 and 4.

By adopting the arrangement of axes shown in FIG. 6, it is also possibleto rotate the blade 4 in such a way that, whilst a dose 50 is cut, aportion of the cutting edge 53 that interacts with the plastics has aspeed component along the exit direction Z1 that is equal to or greaterthan the exit speed V of the flowable material from the extruding device2.

Furthermore, it is possible to ensure that a region of the blade 4 thatinteracts with the plastics after the cutting edge 53 has a speedcomponent along the exit direction Z1 that is the same as or greaterthan the exit speed V with which the flowable material exits from theextruding device 2. In this way the region of the blade 4 that interactslast with the plastics is prevented from pushing the plastics exitingfrom the extruding device 2 to the dispensing opening 8. By suitablychoosing the values of the angles σ, ρ, φ, and ξ it is possible tominimise the contact between the blade 4 and the plastics when a dose 50is cut and in particular ensure that the blade 4 contacts the plasticssubstantially only along the cutting edge 53. This enables theadvantages previously disclosed with reference to FIGS. 3 and 4 to beobtained.

The electric motor 31 can be controlled by electronic speed-varyingmeans that enables the speed W′ of the cutting means 3, and more inparticular of the knife 22, to be varied along the path thereof aroundthe longitudinal axis L. In particular, the electric motor 31 can be aservomotor, i.e. a motor linked, for example, to a further motor thatdrives the moulding carousel 26 or the second transferring means 24.

FIG. 7 is a graph that shows schematically how the speed W′ varies infunction of the time t. At an initial instant t0, in which the knife 22separates the dose 50 from the plastics exiting from the extrudingdevice 2, the speed W′ is the same as a maximum value Wmax.Subsequently, the electronic speed-varying means slows down the knife22, the speed of which W′ reaches a minimum value Wmin in anintermediate instant t1. After the intermediate instant t1, the speed W′increases until maximum value Wmax is reached again at the final instantt2, immediately before starting to cut a new dose 50 of plastics.

Owing to the electronic speed-varying means, it is possible to easilymodify the maximum value and the minimum value of the speed W′,depending on needs. In particular, the value of the speed W′ that thecutting means 3 has when it cuts the dose 50 can be selected in functionof the type of plastics constituting the dose 50 and of the temperaturethereof. Furthermore, by modifying the speed W′ of the cutting means 3it is possible to vary the period of time that elapses between thecutting of two subsequent doses, i.e. to modify the length of the dose50. It should be noted that the electronic speed-varying means enablesthe speed W′ of the cutting means 3 to be varied in a very rapid andsimple manner without the need to replace mechanical parts.

Furthermore, owing to the electronic speed-varying means, the speed W′of the cutting means 3 can be made non-positive, i.e. it may assume nilvalues or values that are less than zero. On the other hand, by usingthe elliptical toothed wheels disclosed in U.S. Pat. No. 4,640,673 thespeed of the knives was able to assume only positive values.

In particular, in the embodiment shown in FIG. 8, the speed W′ of theknife has a minimum value W′min that is equal to zero. This means thatthe knife 22, after cutting the dose 50 by moving at a maximum speedW′max, is slowed down until it stops. After stopping, the knife 22 isaccelerated until the speed thereof again reaches the maximum valueW′max at the final instant t2, in which a new dose 50 can be cut.

In a further embodiment, shown in FIG. 9, the speed W′ of the knife 22is variable between a maximum value W″max that is greater than zero anda minimum value W″min that is less than zero. In this case, the knife22, after cutting the dose 50 by moving at the maximum speed W″max, isslowed down until it stops and is then moved back along the paththereof. After the speed thereof has reached the minimum value W″min,the knife 22 is accelerated until the maximum speed W″max that itreaches immediately before cutting a new dose 50.

By using a knife 22 that moves at a speed of the type shown in FIGS. 7to 9, it is possible to cut the plastics in a clean manner and obtaindoses that are free of burrs. In fact, when the knife 22 cuts theplastics, it moves in a fast manner, which enables a clean cut to beobtained. After cutting the plastics, the knife 22 slows down, whichenables the knife 22 to “waste time”, so to speak, whilst a quantity ofplastics that is sufficient to form a dose 50 exits from the extrudingdevice 2. This effect is particularly accentuated if the knife 22 isstopped between the cutting of a dose and the cutting of the subsequentdose, as shown in FIG. 8, or is moved backwards, as shown in FIG. 9.

Furthermore, by moving the knife 22 backwards it is possible to increasethe space along which the knife 22 can accelerate before cutting a newdose 50. In this way, when it interacts with the plastics exiting theextruding device 2, the knife 22 may have a very great acceleration,which enables it to cut the plastics in a clean and precise manner,without undesired tears or stretches.

Lastly, it should be noted that by using electronic speed-varying meansit is possible to move the knife 22 at a constant speed when cutting adose 50.

The electronic speed-varying means that enables the speed of the knife22 to be varied as shown in FIGS. 7 to 9 can be used not only withcutting means 3 of the type shown in FIG. 5, but also with cutting meansthat moves perpendicularly to the exit direction of the plastics fromthe extruding device 2. On the other hand, the cutting means 3 shown inFIGS. 5 and 6 can also be moved at a constant speed.

As shown in FIG. 10, the supporting element 5 may have an elongated flatshape and be provided with an end at which the blade 4 is removablyfixed, for example through screws 25. At a further end of the supportingelement 5, opposite the aforementioned end, there is obtained a fixinghole 47 through which the supporting element 5 can be fixed to the motorshaft 32.

The cutting means 3 may be provided with a cooling circuit 10 in which acooling fluid, for example water, may circulate. The cooling circuit 10comprises a cooling conduit 11, made in the blade 4, a supply conduit 12and a discharge conduit 13

The supply conduit 12 and the discharge conduit 13 are connectedtogether by means of the cooling conduit 11 and enable the cooling fluidrespectively to reach, and to move away from, the blade 4. The supplyconduit 12 is connected to an inlet of the cooling fluid by means of aninlet connector 48, whilst the discharge conduit 13 is connected to anoutlet of the cooling fluid by means of an outlet connector 49.

The blade 4 comprises a first laminar part 41 and a second laminar part42, shown respectively in FIGS. 11 and 12. The first laminar part 41 andthe second laminar part 42 have substantially the same plan shape andare provided respectively with a first internal face 54 and with asecond internal face 55 that, in an assembled condition shown in FIG.10, are arranged in contact together. The first laminar part 41 and thesecond laminar part 42 comprise respectively a first cutting portion 51and a second cutting portion 52, which in the assembled condition definea cutting edge zone 153 that cuts the dose 50. On the first internalface 54 there is obtained an open channel 56, which is defined by agroove having a plan shape that is substantially like that of an opentriangle. The open channel 56 is provided with a plurality ofrectilinear portions comprising a cooling portion 57 that extends nearto the first cutting portion 51 and is substantially parallel to thefirst cutting portion 51. In the assembled condition, the open channel56 is closed by the second laminar part 42 in such a way as to form thecooling conduit 11.

In order to prevent leaks of cooling fluid, between the first laminarpart 41 and the second laminar part 42 there can be interposed a seal19, consisting for example of a flat element in elastomeric material,having a shape corresponding to the shape of the open channel 56. Inthis case, on the first laminar part 41 there can be obtained a seat 18for housing the seal 19. The open channel 56 is made in the bottom ofthe seat 18. In the assembled condition of the cutting means 3, the seal19 is compressed between the first laminar part 41 and the secondlaminar part 42, preventing leaking of the cooling fluid.

The supply conduit 12 leads into the cooling conduit 11 through a firstpassage opening 14. Similarly, the discharge conduit 13 is connected tothe cooling conduit 11 through a second passage opening 15. The firstopening 14 and the second opening 15 are made in the second laminar part42.

In an embodiment that is not shown, the cooling conduit 11 can be madeof two opposite open channels, which are obtained respectively in thefirst laminar part 41 and in the second laminar part 42.

The cooling circuit 10, through which the cooling fluid flows, enablesthe temperature of the cutting means 3 to be diminished effectively,especially at the cutting edge zone 153 of the blade 4. In this way itis possible to significantly reduce the phenomena of adhesion of theplastics to the blade 4 during cutting, enabling the dose 50 to be cutin a precise and clean manner. Furthermore, the decrease of thetemperature and of the phenomena of adhesion enables wear anddeterioration of the cutting means 3 to be limited, in particular of thefirst cutting portion 51 and of the second cutting portion 52.

In an embodiment that is not shown, the cutting means 3 can be providedwith heating means for heating the blade 4, particularly near thecutting edge zone 153. The heating means can comprise a heating circuit,structurally similar to the circuit 10 shown in FIGS. 10 to 12, in whichthere circulates a heated fluid. Alternatively, the heating means maycomprise an electrical resistance or any other known type of heatingdevice. The heating means is such as to heat the blade 4 to atemperature that is greater than the melting temperature of the plasticsexiting from the extruding device 2. In particular, if the heating meansheats the blade 4 to a temperature little greater than theaforementioned melting temperature, the plastics cut by the cuttingmeans 3 cannot solidify on contact with the blade 4 and deposit on thelatter. In this way, residues of plastics are prevented from forming onthe blade that could compromise cutting precision. If on the other handthe heating means heats the blade 4 to a temperature much greater thanthe melting temperature of the plastics, possible deposits of plasticsthat have accumulated on the blade 4 are thermally degraded andvolatilised.

As shown in FIGS. 13 and 14, the apparatus 1 may comprise divertingmeans 6 that is able to discard a possible defective dose 50′ bydiverting the latter from the exit direction Z1 along which the plasticsexit from the extruding device 2.

The diverting means 6 comprises one or more nozzles 16, which arepositioned below the cutting means 3 and are suitable for emitting jets30 of pressurized fluid, typically compressed air, intended to hit thedefective dose 50′. The jets 30 have a pressure that is able to developa sufficient thrust to project the defective dose 50′ far from theextruding device and from the cutting means 3, as well as from thetransferring means 9. For example, in the case of FIGS. 13 and 14 thedefective dose 50′ is projected outside the first carousel 23. Thediverting means 6 thus prevents the defective dose 50′ from reaching thecorresponding first transferring element 101 of the first transferringmeans 100. The diverting means 6 can be used in the start-up steps ofthe apparatus 1 to discard possible defective doses 50′ having a lengthin the exit direction Z1 that is less than a preset limit. Such dosesare not correctly conveyable by the transferring means 9. In fact, theaforementioned doses could arrange themselves transversely to the exitdirection Z1 whilst they traverse the funnel elements of the firsttransferring means 100. If this occurs, the defective doses 50′ wouldocclude the funnel elements, making it necessary to arrest the apparatus1 to remove them from the funnel elements.

FIG. 15 shows an embodiment of the apparatus 1 in which there isprovided discarding means 58 for discarding a possible defective dosewhilst the latter is conveyed by the transferring means 9, and inparticular by the second transferring means 24. The discarding means 58is activatable when it is detected that the extruding device 2 hasdispensed a dose that, although having a sufficient length to make itconveyable by the transferring means 9, is nevertheless not free ofdefects. The discarding means 58 may comprise for example a pneumaticdevice, similar to the nozzles 16 disclosed with reference to FIGS. 13and 14, which pushes the defective dose outside the discarding means 58can expel the defective dose 50′ through the lower end of thecorresponding second transferring element 27, which the closing meanspreviously opened.

The discarding means 58 is positioned upstream of the deliveringposition R with respect to a movement direction M of the secondtransferring means 24. In this way, when the defective dose isdiscarded, the second transferring means 24 has a relatively lowacceleration, as will be explained better below.

In the second path P2 of the second transferring means 24 it is possibleto define a portion T1 substantially coinciding with an arc of the firstpath P1 of the first transferring means 100. Along the portion T1 eachfirst transferring element 101 is substantially superimposed on acorresponding second transferring element 27, so as to a relatively long5 period of time is available during which the dose 50 can pass from thefirst transferring element 100 to the second transferring element 27.

Similarly, it is possible to define a further portion T2 in which thesecond path P2 of the second transferring means 24 and the third path P3of the forming means 17 are substantially coincident. In the furtherportion T2, the dose 50 has a relatively long period of time availablefor being transferred from the second transferring means 24 to theforming means 27.

In the portion T1, the speed of the second transferring means issubstantially the same as the speed of the first transferring means 100.Similarly, in the further portion T2 the speed of the secondtransferring means 24 is substantially the same as the speed of theforming means 27.

Between the portion T1 and the further portion T2 there is defined adeparture curved portion C1 in which the acceleration of the secondtransferring means 24 is maintained below a limit value to preventexcessive stress to the dose 50, which in this zone is contained insidea corresponding second transferring element 27. Between the furtherportion T2 and the portion T1 there is defined a return curved portionC2 in which the acceleration of the second transferring means 24 ishigher inasmuch as there exists no risk of damaging the doses 50, whichhave already been delivered to the forming means 17. This furthermoreenables the overall dimensions of the second transferring means 24 to bekept limited in the return curved portion C2. By positioning thediscarding means 58 between the portion T1 and the further portion T2,i.e. in the departure curved portion C1, the discarding of the defectivedoses is made easier. In fact, the discarding means acts in a zone ofthe second path P2 in which the acceleration of the second transferringmeans 24 is kept at relatively low values. It is not therefore necessaryto slow down the second transferring means 24 in order to make thediscarding possible.

In an embodiment that is not shown, in the departure curved portion C1it is possible to define a portion in which the second transferringmeans 24 has a constant speed and therefore zero acceleration. In thiscase, the discarding means 58 is positioned in the constant speedportion, in which it is easier to discard a possible defective dose 50′as no inertia forces act thereupon.

In an embodiment, the apparatus 1 may comprise both the discarding means58 and the diverting means 6. In this case, the diverting means 6 isused to discard the defective doses 50′ dispensed in the start-up stepsof the apparatus 1. These doses may in fact be too short and thereforenot be conveyable by the transferring means 9. The discarding means 58is on the other hand used to discard possible defective doses that areproduced when the apparatus 1 is running normally. These doses areusually of sufficient length to be conveyed by the transferring means 9,whilst having defects that would not enable a preform of good quality tobe obtained.

In an alternative embodiment, the apparatus 1 may comprise only thediscarding means 58 and be devoid of the diverting means 6. This ispossible, for example, when the extruding device 2 is provided with apositive displacement pump that pushes the plastics to the dispensingopening 8. The positive displacement pump in fact enables asubstantially constant flow rate of plastics to be obtained, which makesthe risk almost nil of obtaining doses that are so short as not to beconveyable by the transferring means 9.

It has been seen experimentally that if the extruding device is providedwith a positive displacement pump, in the start-up steps of theapparatus 1 possible defects are concentrated in a preset number ofinitial doses dispensed through the dispensing opening 8, usuallycomprised between five and ten initial doses. It is thus possible to setup the discarding means 58 in such a way as to automatically discard afixed number of initial doses in the start-up steps of the apparatus 1.This enables complicated controls to be avoided that are intended todetermine when the extruding device 2, during the start-up steps of theapparatus 1, starts to dispense doses of acceptable quality.

It is understood that the features disclosed in the description of theFigures with reference to a specific embodiment can be claimed also inrelation to any other disclosed embodiment or also per se.

1.-132. (canceled)
 133. Apparatus comprising an extruding device havinga dispensing opening for extruding a flowable material in an exitdirection through said dispensing opening, a transferring arrangementfor transferring a dose of said flowable material to a formingarrangement, a cutting arrangement interposed between said extrudingdevice and said transferring arrangement for separating said dose fromsaid flowable material and a driving arrangement for rotating saidcutting arrangement, said cutting arrangement having a cutting edge thatis oblique with respect to said exit direction so that said cuttingarrangement periodically passes between said extruding device and saidtransferring arrangement with a motion component that is parallel tosaid exit direction and a further motion component that is perpendicularto said exit direction.
 134. Apparatus according to claim 133, whereinsaid motion component is directed in such a way as to move said cuttingarrangement away from said dispensing opening whilst said dose is beingseparated.
 135. Apparatus according to claim 133, wherein said drivingarrangement comprises a motor having a motor shaft extending along alongitudinal axis.
 136. Apparatus according to claim 135, wherein saidmotor is an electric motor.
 137. Apparatus according to claim 135,wherein said longitudinal axis is skew with respect to an exit axisalong which said flowable material exits from said dispensing opening,said exit axis being parallel to said exit direction.
 138. Apparatusaccording to claim 137, wherein said exit axis is vertical. 139.Apparatus according to claim 137, and further comprising a spacingelement interposed between a flange of said driving arrangement and asupporting element for fixing said driving arrangement to a frame ofsaid apparatus.
 140. Apparatus according to claim 139, wherein saidspacing element is delimited by a first face that is in contact withsaid flange and by a second face that is in contact with said supportingelement, said first face being tilted with respect to said second face.141. Apparatus according to claim 139, wherein said flange (33) issubstantially perpendicular to said longitudinal axis and saidsupporting element defines a supporting plane for said spacing element,said supporting plane being substantially perpendicular to said exitaxis.
 142. Apparatus according to claim 135, wherein said cuttingarrangement comprises a cutting element that lies on an oblique planewith respect to said longitudinal axis.
 143. Apparatus according toclaim 142, wherein said cutting edge is made in said cutting element andis lying on said oblique plane.
 144. Apparatus according to claim 142,wherein said longitudinal axis is skew with respect to an exit axisalong which said flowable material exits from said dispensing opening,said exit axis being parallel to said exit direction and said obliqueplane is perpendicular to an axis that intersects said longitudinal axisat a point of said oblique plane, said axis being skew with respect tosaid exit axis.
 145. Apparatus according to claim 135, and furthercomprising a separating element interposed between a first plate fixedwith respect to said motor shaft and a second plate fixed with respectto said cutting arrangement.
 146. Apparatus according to claim 145,wherein said separating element is delimited by a first surface that isin contact with said first plate and by a second surface that is incontact with said second plate, said first surface being tilted withrespect to said second surface.
 147. Apparatus according to claim 133,wherein said driving arrangement comprises electronic speed-varyingdevices for modifying a rotation speed of said cutting arrangement. 148.Apparatus according to claim 147, wherein said electronic speed-varyingdevices are configured in such a way as to vary said rotation speedbetween a minimum value and a maximum value.
 149. Apparatus according toclaim 148, wherein said minimum value is nil.
 150. Apparatus accordingto claim 148, wherein said minimum value is negative.
 151. Apparatusaccording to claim 133, and further comprising a cooling circuit forcooling said cutting arrangement.
 152. Apparatus according to claim 151,wherein said cutting arrangement comprises a first lamina-shaped partand a second lamina-shaped part between which there is defined a conduitof said cooling circuit.
 153. Apparatus according to claim 152, whereinon said first lamina-shaped part there is obtained an open channelsuitable for being closed by said second lamina-shaped part to definesaid conduit.
 154. Apparatus according to claim 152, wherein saidconduit substantially has an open-triangle plan shape.
 155. Apparatusaccording to claim 152, wherein said conduit comprises a cooling portionthat is arranged near to a cutting edge zone of said cuttingarrangement.
 156. Apparatus according to claim 155, wherein said coolingportion is substantially parallel to said cutting edge zone. 157.Apparatus according to claim 152, wherein said first lamina-shaped partand said second lamina-shaped part form, in an assembled condition, ablade of said cutting arrangement, said blade being removably fixed to asupporting element.
 158. Apparatus according to claim 152, wherein saidcooling circuit comprises a supply conduit and a discharge conduit bymeans of which a cooling fluid can respectively enter, and exit from,said conduit.
 159. Apparatus according to claim 158, wherein said firstlamina-shaped part and said second lamina-shaped part form, in anassembled condition, a blade of said cutting arrangement, said bladebeing removably fixed to a supporting element and said supply conduitand said discharge conduit are made in said supporting element. 160.Apparatus according to claim 158, wherein said second lamina-shaped parthas a first opening through which said supply conduit leads into saidconduit.
 161. Apparatus according to claim 160, wherein said secondlamina-shaped part has a second opening through which said dischargeconduit is in fluid communication with said conduit.
 162. Apparatusaccording to claim 133, wherein said cutting arrangement is providedwith a heating arrangement for heating an operating surface of saidcutting arrangement, said operating surface being suitable forinteracting with said flowable material.
 163. Apparatus according toclaim 162, wherein said heating arrangement comprises a circuit in whicha heated fluid can circulate.
 164. Apparatus according to claim 162,wherein said heating arrangement comprises an electrical resistancedevice.
 165. Apparatus according to claim 133, and further comprisingdiscarding devices for discarding a defective dose.
 166. Apparatusaccording to claim 165, wherein said discarding devices comprisediverting devices for diverting said defective dose from said exitdirection.
 167. Apparatus according to claim 166, wherein said divertingdevices comprise at least one nozzle for emitting a jet of pressurisedfluid that hits said defective dose.
 168. Apparatus according to claim167, wherein said at least one nozzle comprises at least one pneumaticnozzle for emitting compressed air.
 169. Apparatus according to claim133, wherein said transferring arrangement is arranged for receivingsaid dose cut by said cutting arrangement in a removal position anddelivering said dose to said forming arrangement in a delivery position.170. Apparatus according to claim 169, wherein said discarding devicescomprise diverting devices for diverting said defective dose from saidexit direction and said diverting devices are interposed between saidcutting arrangement and said transferring arrangement to prevent saiddefective dose from reaching said transferring arrangement. 171.Apparatus according to claim 169, and further comprising discardingdevices for discarding a defective dose wherein said discarding devicesare arranged upstream of said delivery position to remove said defectivedose from said transferring arrangement.
 172. Apparatus according toclaim 169, wherein said transferring arrangement comprises a firsttransferring arrangement for receiving said dose in said removalposition and a second transferring arrangement for receiving said dosefrom said first transferring arrangement and delivering it to saidforming means.
 173. Apparatus according to claim 172, and furthercomprising discarding devices for discarding a defective dose saiddiscarding devices being positioned along a path of said secondtransferring arrangement to expel said defective dose from said secondtransferring arrangement upstream of said delivery position. 174.Apparatus according to claim 133, wherein said forming arrangement arearranged for compression-moulding said dose.
 175. Apparatus according toclaim 174, wherein said forming arrangement comprises a plurality ofmoulds mounted in a peripheral region of a rotatable carousel. 176.Apparatus according to claim 174, wherein said forming arrangementcomprises a die device interacting with a punch device to form acontainer preform from said dose.
 177. Apparatus according to claim 133,wherein said cutting arrangement comprises a single knife.
 178. Methodcomprising extruding a flowable material along an exit direction througha dispensing opening of an extruding device, separating a dose from saidflowable material by using a rotating cutting arrangement having acutting edge that is oblique with respect to said exit direction andtransferring said dose to a forming arrangement by using a transferringarrangement, wherein during said separating said cutting arrangementpasses between said extruding device and said transferring arrangementwith a motion component that is parallel to said exit direction and afurther motion component that is perpendicular to said exit direction.179. Method according to claim 178, wherein said motion component isdirected in such a way that, whilst said dose is being cut, said cuttingarrangement moves away from said dispensing opening.
 180. Methodaccording to claim 179, wherein, during said separating, a cutting edgezone of said cutting arrangement has a speed component along said exitdirection that is substantially equal to an exit speed of said flowablematerial from said dispensing opening.
 181. Method according to claim179, wherein, during said separating, a cutting edge zone of saidcutting arrangement has a speed component along said exit direction thatis greater than an exit speed of said flowable material from saiddispensing opening.
 182. Method according to claim 180, wherein, duringsaid separating, a zone of said cutting arrangement interacting withsaid flowable material after said cutting edge zone has a respectivespeed component along said exit direction that is substantially equal tosaid exit speed.
 183. Method according to claim 180, wherein, duringsaid separating, a zone of said cutting arrangement interacting withsaid flowable material after said cutting edge zone has a respectivespeed component along said exit direction that is greater than said exitspeed.
 184. Method according to claim 178, wherein said cuttingarrangement is rotated around a longitudinal axis that is skew withrespect to an exit axis along which said flowable material exits fromsaid extruding device during said extruding, said exit axis beingparallel to said exit direction.
 185. Method according to claim 184,wherein said cutting arrangement comprises a cutting element that liessubstantially on a plane that is oblique with respect to saidlongitudinal axis.
 186. Method according to claim 178, wherein saidflowable material is plastics.
 187. Method according to claim 178, andfurther comprising compression-moulding said dose by using said formingarrangement.
 188. Method according to claim 187, wherein saidcompression moulding comprises obtaining a container preform from saiddose.